By Sarah Mukherjee
BBC environment correspondent
The elusive hazel dormouse spends most of its life asleep
A conservation charity has urged the public to scour woodlands for half-eaten hazelnuts to help track down and record the whereabouts of the elusive, endangered dormouse.
It is one of the glories of the British autumn - a walk in the woodland.
The deep scent of moss and damp soil, the dappled light, and of course the colours of the leaves, from burnt raspberry to caramel to the palest gold.
The trees at Burnham Beeches near Slough are beginning to show this spectacular display, as we wander through the woods in the lilac light of morning.
But the People's Trust for Endangered Species is hoping woodland walkers this weekend will not have their eyes on the canopy above, but on the ground below.
They are urging us all to take part in the Great Nut Hunt and look for hazelnut shells that bear signs of one of Britain's rarest mammals.
The hazel dormouse is difficult to find at the best of times - mainly because it spends most of its time asleep (Lewis Carroll's depiction of the dormouse as the permanently sleepy guest at the Mad Hatter's Tea Party was not far off the mark).
The mammal is in danger of extinction
Small and brown, with large shiny black eyes, a distinctive bushy tail and large, bushy whiskers, they are cute but elusive - nocturnal and living most of the time up a tree.
They awake in mid-April to breed and feed for a few months, preferring the hazelnuts that give them their name.
"They chew a little hole in the side of the nut and then suck out the contents. It's very distinctive. It looks like a hole's been drilled in the side," says Dr Pat Morris, an internationally-regarded expert on the dormouse.
The self-proclaimed Chief Nutter for the Hunt added: "What we want people to do is collect nuts that have these markings, send them to us saying when and where they were found, and we can then compile the information."
Chief executive of the Trust, Jill Nelson, said: "The results we get from the survey are very valuable. The dormice are incredibly difficult to see.
"But if we know where they are from the survey, we can put conservation measures in place to protect them."
And there is another incentive. The Trust has hidden 20 silver replica hazelnuts, and a gold-plated one, across England and Wales for would-be "nutters" to find.
Survey packs are available from the Trust.